You have configured the ability for an xDB contact to be associated with

a CRM account. Now you must create a Sitecore template that can be used
to store information about the CRM account.

Having Sitecore items that represent CRM accounts will allow your users
to configure rules based on account membership. For example, a marketer
will be able to personalize a web page based on whether or not a visitor
is associated with a specific account.

The marketer must be able to select from a list of available accounts.
This is the purpose of exposing CRM accounts as Sitecore items.